A semiconductor wafer of, for example, silicon or gallium arsenide is produced in a large diameter, cut and separated (diced) into elemental chips and subjected to the subsequent mounting step. In this process, the semiconductor wafer undergoes dicing, cleaning and drying steps in the state of being attached to a pressure sensitive adhesive sheet and is transferred to the subsequent pickup and mounting steps. It is desired that the above pressure sensitive adhesive sheet employed in the steps from the semiconductor wafer dicing to the pickup have an adhesive strength which is so large as to securely hold the wafer (chips) in the dicing to drying steps but which is on such a level that no adhesive remains to the wafer (chips) in the pickup step. This type of pressure sensitive adhesive sheet was proposed in, for example, Japanese Patent Laid-open Publication Nos. 60(1985)-196956 and 60(1985)-223139. In the proposed pressure sensitive adhesive sheets, however, it was practically infeasible to completely nullify the adhesive strength (vertical peeling strength) at the pickup step and, irrespective of the efforts for reduction, the vertical peeling strength at the pickup step encountered a limit of about 100 to 300 g/10 mm sq. Therefore, in actually carrying out the above process, not only are the chips pushed upward from the back of the pressure sensitive adhesive sheet by means of a thrust needle to thereby separate the chips from the pressure sensitive adhesive sheet but also pickup of the chips is performed with the use of a suction collet.
Recently, various electronic components (chips) for preventing stealth and forgery are assembled into cards, for example, ID, memory, credit and cash cards. It is required that the electronic components to be assembled in these cards have very small thickness and have large surface area relative to the thickness so as to have large capacity.
The problem has surfaced such that the use of the above thrust needle in the pickup of chips of small thickness and large surface area would break the chips to thereby gravely lower the chip yield.
The present invention has been made with a view toward resolving the above problem of the prior art. An object of the present invention is to provide a process for producing a chip in which chips of small thickness and large surface area can easily be picked up, and another object of the present invention is to provide a pressure sensitive adhesive sheet suitable for use in the above process. That is, objects of the present invention are to provide a process for producing a chip in which chips can be picked up without the need to use any thrust needle and to provide a pressure sensitive adhesive sheet suitably employed in the above process.